Distance estimation is of relevance for several applications involving electronic appliances having optics systems and cameras. Some applications may need to determine an object distance to correct for axial chromatic aberration in the image obtained by the camera. In other applications of electronic appliances, distance estimation may be used for surveillance purposes and/or may be useful for safety control mechanisms, to ensure that appropriate safety measures are satisfied.
Current approaches to distance estimation for optics systems and cameras make use of active methods involving intensive adjustment of the optics system. In current approaches to active methods, an optics system configuration is continuously modified while an image is captured and a “sharpness” metric is obtained. A feedback mechanism usually provides information to a mechanical actuator to scan for a configuration that maximizes the sharpness metric selected. In such systems, the configuration of the optical system is usually adjusted until the sharpest point is obtained. The appliance then evaluates the object distance by using a processor to retrieve the object distance from a pre-selected through-focus sharpness graph.
One of the drawbacks of using this approach is the distraction to the sharpness metric introduced by the presence of physical objects between the object of interest and the camera. For example, a glass or a tree may create complicating features for the sharpness metric.
Another drawback of current active systems is that normally a continuous scan of optical system configurations is necessary, adding stringent requirements to a mechanical actuator. In some instances, a feedback mechanism is necessary to couple the mechanical actuator to a metric optimization. This may add an extra design requirement for the electronics included in the appliance. Furthermore, the time it takes to find an object distance by continuously scanning for an optimal configuration may be excessive. This may be especially burdensome for integrated systems where finding the object distance may be only one task in a series of more complex operations.
As a result, there is a need for an electronic appliance that performs distance estimation accurately and with few mechanical requirements that can be flexibly adapted to more complex systems.